There are several procedures available to patients with degenerative spine conditions. For example, Anterior Lumbar Interbody Fusion (“ALIF”) has been performed by surgeons since the 1950's. In an ALIF procedure, the disc space is fused by approaching the spine through the abdomen. In the ALIF approach, a three-inch to five-inch incision is made on the left side of the abdomen and the abdominal muscles are retracted to the side. Since the anterior abdominal muscle in the midline (rectus abdominis) runs vertically, it does not need to be cut and easily retracts to the side. The abdominal contents lay inside a large sack (peritoneum) that can also be retracted, thus allowing the spine surgeon access to the front of the spine without actually entering the abdomen. There is also a less popular transperitoneal approach that accesses the spine through the abdomen. This adds a lot of unnecessary morbidity to the procedure and therefore is used much less often.
Another technique is called Posterior Lumbar Interbody Fusion (“PLIF”). In the PLIF approach, the spine is accessed through a three-inch to six-inch long incision in the midline of the back and the left and right lower back muscles are stripped off the lamina and spinous process on both sides and at multiple levels. After the spine is approached, the lamina and spinous process is removed, which allows visualization of the nerve roots. The facet joints, which are directly over the nerve roots, may then be undercut to give the nerve roots more room. The nerve roots are then refracted to one side and the disc space is cleaned of the disc material. A bone graft, or an interbody cage, is then inserted into the disc space and the bone grows from vertebral body to vertebral body.
Still another procedure is a Transforaminal Lumbar Interbody Fusion (“TLIF”). By removing the entire facet joint, visualization into the disc space is improved and more disc material can be removed. It should also provide for less nerve refraction. Because one entire facet is removed, it is only done on one side. Removing the facet joints on both sides of the spine would result in too much instability. With increased visualization and room for dissection, a larger implant and/or bone graft can be used. Although this has some improvements over a PLIF procedure, the anterior approach, in most cases still provides the best visualization, most surface area for healing, and the best reduction of any of the approaches to the disc space.
There are other approaches know in the art, as well. For instance, Direct Lateral Interbody Fusion, Axial Lumbar Interbody Fusion using a transsacral approach, and the like. Those skilled in the art will appreciate that these and other known procedures have benefits, as well as disadvantages.
There are also many types of stabilization systems available. One type of spinal stabilization system includes screws and connecting rods which can be used for stabilizing many spinal conditions including, for example, degenerative disc disease, scoliosis, spondylolithisis and spinal stenosis. In these systems, a bone screw (e.g., pedicle screw) is typically anchored into each vertebral body to be stabilized and a rigid connecting rod mounted to the screws to fix the vertebrae in a particular relative position.
Another type of spinal stabilization system includes interbody implants. Some of these implants are bone, PEEK, solid titanium or similar non-bone implant material and some are hollow implants that provide for inclusion of a bone graft or other suitable material to facilitate bony union of the vertebrae.
Interbody implants can be inserted into the disc space through an anterior, posterior or lateral approach. In some systems, the implants are inserted into a bore formed between adjacent vertebral bodies in the cortical endplates and can extend into the cancellous bone deep to the cortical endplates. Implant size is typically selected such that the implants force the vertebrae apart to cause tensing of the vertebral annulus and other soft tissue structures surrounding the joint space. Tensing the soft tissues surrounding the joint space results in the vertebrae exerting compressive forces on the implant to maintain the implant in place.
Accordingly, there is a continuing need for improved vertebral stabilizing devices and methods. The system and apparatuses described herein are directed to addressing these needs.